“Aesthenopia” means a state in which unidentified complaint-like constitutional symptoms such as stiffness in the shoulders or waist, or irritation, etc., appear with the symptoms such as pain and dim of eyes as a result of exploitation of eyes, and one feels fatigue on carrying out an activity even when it can be easily done in a usual state.
As eye diseases, astigmatism, myopia, cataract, glaucoma, etc., have been known, which are caused by hypofunction or malfunction such as aging of eye hall portion, etc., and a treatment therapy can give an effect by eyeglasses or an operation. On the other hand, for a contemporary person, a chance to watch a television or a display of an OA equipment such as a personal computer for a long period of time increases in a home or one's workplace everyday, so that a burden to the eyes markedly increases. Thus, local symptoms such as pain, dim, dazzling or congestion of eyes, and watery eyes, or various constitutional symptoms such as stiffness in the shoulders or waist, irritation, nausea, feeling a heavy head, etc., appear. Aesthenopia is defined to be the conditions that a person is suffered from local symptoms or constitutional symptoms as mentioned above, and the person feels fatigue easily on carrying out a work which can be easily carried out for a healthy person without feeling any fatigue.
Aesthenopia is not a simple eye fatigue, but has characteristics in subsidiary causing various unpleasant symptoms such as stiffness in the shoulders or waist, irritation, nausea, feeling a heavy head, etc.
Human vision (acuity) is an advanced information processing system which is mechanically precise and admits an outer thing as an image through the following mentioned three main steps. (1) A light which is controlled a thickness of the lens and controlled a diaphragm due to high-speed muscular movement of the ciliary body is passed through lens and crystalline lens of eyeball and reached to the retina, (2) the light is converted into an electrical signal through the rod and the cone of the retina, and sent to the visual cortex of the brain through the nerve, and (3) information processing is carried out at the visual cortex to admit it as an image. It is the advanced information processing system which passed through the above-mentioned three steps. The detailed mechanisms are complicated and have not yet been known well. The so-called vision is a function exhibited as a compilation of these functions. It is thought that vision is lowered even if any one of the functions of these three steps is lowered. It has been considered that fatigue is caused as a result of the above, but the onset mechanisms of the aesthenopia having the above-mentioned complicated symptoms, etc., have not yet been known well.
However, in recent years, a person who complains such symptoms is increasing particularly in working young women, so that a health food or a medicine which treats, prevents and improves aesthenopia have been strongly demanded.
As a medicine which professes treatment effects of aesthenopia, Class III medicines such as vitamin B1 agent (ALINAMIN (Takeda Pharmaceutical Co., Ltd.)) and total vitamin agent (QP GOLD KOWA (KOWA Company Ltd.)) are commercially sold for general uses. However, these medicines are approved by merely expecting an anti fatigue effect from a supplemental nutrient function of vitamin B1 as a vitamin. Thus, the effect was approved with a wider scope without any sufficient clinical test as far as aesthenopia is concerned, so that it is the actual situation that they do not show any sufficient effect on the aesthenopia irrespective of the expectation.
Vitamin B1 series medicines had been approved on the effects such as pain relief accompanied by neural transmission, muscular pain, fatigue, etc., from the association that vitamin B is concerned with neural transmission without any sufficient evidence from the viewpoint of modern science, whereas it is unavoidable on a science level of those days. Thus, they are insufficient in the effect and efficacy.
On the other hand, chondroitin sulfate has been admitted to as a medicine and used. That is, sodium chondroitin sulfate has been used as a medicine for the treatment of lumbar pain, joint pain, scapulohumeral periarthritis (frozen shoulder), etc., as an injection solution, and for the protection of a cornea outer layer as an eye drop, and as a medicine for general purpose, it has been used for joint pain and nerve pain as an oral medicine. However, it has never been used for the treatment of aesthenopia as of today.
A food having an effect of improving eye function such as improvement in aesthenopia, etc., has been known, for example, astaxanthin, a blueberry extract, a marigold extract, docosahexaenoic acid, etc. These are formulated in a health food, etc. (Patent literatures 1 to 4).
However, the supplement or the health food into which these eye function-improving agents are formulated shows an effect of improving aesthenopia with a certain extent, but the effect cannot be said to be sufficient, whereby a medicine or a composition of a food and a drink having more excellent treatment, prophylaxis and improved effect of aesthenopia has been demanded.